The present invention relates to a positioning device that can position or locate a member relative to the other member with higher accuracy. The invention also relates to a positioning device for a linear bearing or a guide apparatus for relatively slidably supporting an axially extending shaft member and a column receiving the shaft member.
In a machine tool, a conventional way to index one member relative to another member and position or locate it is to use a knock pin of which one end or particularly the distal end protrudes vertically from a contact surface of one of the two members, or to use triangular shaped teeth such as a serration or trapezoidal shaped teeth that are formed on both of the members.
In the case of a knock pin, especially a straight pin, when a distal end of the pin is fitted into a hole with a clearance fit, detachment of the pin from the hole becomes easy but positioning or locating of the two members with accuracy becomes difficult due to a clearance created between the pin and the hole. To the contrary, when a distal end of the pin is fitted into a hole with an interference fit, positioning or locating with accuracy becomes possible but attachment as well as detachment of the pin from the hole becomes difficult due to a tight fit of the distal end of the pin relative to the hole, thereby making coupling and decoupling of the two members difficult.
In the case of triangular or trapezoidal shaped teeth, positioning is achieved by contacting each tapered surface of a pair of opposed teeth between the two members. However, in this case, it is not easy to engage the tapered surfaces of the whole opposed teeth with each other with a uniform force, and thus, an index table may be made inclined. As a result, positioning with higher accuracy becomes difficult.
The present invention has been made under those circumstances and its first object is to provide a positioning device with higher accuracy. A second object of the present invention is to facilitate attachment and detachment of the members to be positioned in the positioning device.
On the other hand, a linear guide is conventionally used as a conveying device. A linear guide is generally comprised of a linearly extending rail, and a carriage that is translatable along the rail and that has a slide mechanism to slidably support the carriage on the rail.
In such a linear guide, a carriage needs boring or milling to form a through hole or a through groove for a rail to be inserted thereinto. However, when boring a hole or milling a groove in a carriage of one construction, in the case of a longer carriage, boring or milling cannot be finished in one process, thus necessitating each boring or milling process on opposite ends of the carriage separately. In this case, each center of the holes or the grooves on both ends of the carriage may be offset or shifted, and boring or milling accuracy cannot be secured.
On the other hand, when a longer carriage is formed of a plurality of shorter carriage members that are connected to each other by a through bolt, in the case of a through hole or a through groove of polygonal cross sectional shape, each polygonal cross sectional shape of the carriage members may not be precisely conformed to each other, and similarly, boring or milling accuracy of the carriage cannot be secured. Thus, there were limitations on boring or grooving accuracy and positioning accuracy in a prior art linear guide with a longer carriage.
The present invention has also been made under those circumstances and its third object is to provide a positioning device for a guide apparatus that can produce a longer carriage easily and accurately.
A positioning device according to one aspect of the present invention includes a first member having a first, flat contact surface and a second member having a second, flat contact surface adapted to contact the first contact surface. The first contact surface has a plurality of first grooves formed thereon, each of which extends along the first contact surface and has U-shaped or circular cross section. The second contact surface has a plurality of second grooves formed thereon, each of which extends along the second contact surface, has U-shaped or circular cross section and is disposed at a position corresponding to each of the first grooves. Solid cylindrical positioning pins fitted into the corresponding first and second grooves are in contact with each opening edge of the first and second grooves and they position or locate the first and second members relative to each other.
In this case, since the first and second members are positioned relative to each other through the cylindrical positioning pins disposed along the first and second contact surfaces with the first and second contact members contacted with each other, each contact surface will not be inclined and highly accurate positioning becomes possible.
Also, in this case, each positioning pin fitted into each groove of the first and second member is in linear contact with the opening edge portion of the groove along its generating line, thereby facilitating attachment and detachment of the positioning pin relative to the groove, and thus, coupling and decoupling of the first and second members can become easy.
A positioning device according to another aspect of the present invention is provided for a guide apparatus adapted to slidably support a shaft member and a column or carriage relative to each other. The column has an axially extending through hole or through groove and the shaft member is inserted into the through hole or through groove. A slide mechanism with a plurality of rolling elements is provided between the column and the shaft member to slidably support the column relative to the shaft. The column is formed of a plurality of split members that are divided at sections orthogonal to the axial direction and that are connected to each other. A plurality of supporting grooves each having U-shaped or circular cross section are formed on each contact surface of each adjacent split member, and corresponding supporting grooves are oppositely disposed on the contact surfaces of the adjacent split members. Each split member is positioned or centered by cylindrical positioning pins inserted into the oppositely disposed supporting grooves.
In this case, since the column is composed of a plurality of split members connected to each other in the axial direction, by predetermining an axial length of each split member at an appropriate length that allows for boring or milling with higher accuracy, boring or milling process of each split member can be conducted accurately. Moreover, in this case, since each split member is centered by the positioning pins extending along the contact surfaces, each through hole or through groove of the split members can be centered or located accurately when having composed a column from split members by connecting them in the axial direction. In such a way, a column of a longer length can be manufactured with ease and accuracy.